This invention relates generally to methods and apparatus for diagnostic medical imaging and more particularly to methods and apparatus for automated angiographic analysis. However, the invention is also more generally useful for analysis of other cyclical images.
A coronary angiogram (or synonymously, an arteriogram) is an x-ray of the coronary arteries. Such images help the physician observe blocked arteries for the diagnosis of coronary artery disease. An angiogram is often part of a cardiac catheterization procedure including other tests and measurements. A patient undergoing catheterization also undergoes physiological monitoring. Typically, an electrocardiogram (ECG or, synonymously, EKG) is produced from electrical leads attached to a patient and analyzed to detect irregularities indicative of heart damage or disease. Data from the ECG is stored in a computer database.
To perform an angiogram, a physician injects a contrast medium into the coronary arteries using catheter inserted through a blood vessel (such as a femoral artery) up to the heart and then takes an X-ray of the heart. The angiogram assists the physician in determining the location and severity of coronary artery disease. This information is then used to determine what, if any, treatment is medically appropriate.
Cardiac angiography is performed in a cardiac catheterization laboratory utilizing cardiovascular X-ray imaging equipment. Left ventricular analysis, which is the contour detection of the diastolic and systolic left ventricle, can be carried out by capturing images in which a contrast medium has been injected into the left ventricle.
Images produced by X-ray imaging equipment can be stored on photographic film or electronically as digital images. Typically, digital images are stored in DICOM (Digital Imaging and Communications in Medicine format) and stored and viewed at a workstation.
Cardiac angiography images are usually reviewed as moving pictures. For left ventricular analysis, the perimeter of the dye filled left ventricular chamber is manually or semi-automatically delineated in each portion of the cardiac cycle. Various known analysis methods require a user to manually select a pair of images, more particularly, a diastole and a systole image, draw or mark the contours of the dye filled ventricle. Automatic (i.e., computerized) edge detection is possible, but is often difficult due to lack of edge definition or obscuration by musculature inside the ventricle. More often than not, automated edge detection systems require manual adjustment for successful edge detection for left ventricular analysis.